Metallocene catalysts are widely used to produce polyolefin polymers such as polyethylene polymers. They have provided efficient processes and a variety of new and improved polymers. However, there is continued focus in the industry on developing new and improved metallocene catalyst compositions. Some have focused on designing the catalyst compositions to produce new polymers, others on improved operability, and yet others on improving catalyst productivity. The productivity of a catalyst, that is, the amount of polymer produced per gram of the catalyst, can be an important concern for polyolefin producers. Reactor operability (e.g., lack of fouling and sheeting, etc. of the polymerization reactor) is another major concern for polyolefin producers. Reducing the occurrence of reactor fouling has commercial benefits in reduced down time for the reactor and improved output of polyolefin resin, as well as higher quality resin.
In order to address reactor fouling problems, other additives such as metal carboxylate salts are often added to the catalyst, either separately or as part of the supported catalyst composition. However, such additives can suppress catalyst productivity and resin bulk density.
Thus, it would be advantageous to have an improved polymerization process that utilizes metal carboxylate salts to address reactor fouling problems, for example, without having undesirable suppression of catalyst productivity and resin bulk density.